Sound transducer for dictating equipment



Dec. 7, 1965 R. GORIKE SOUND TRANSDUCER FOR DICTA'IING EQUIPMENT Filed Aug. 21, 1962 F/G2a F/G. 2b

F/G. la

United States Patent firm Filed Aug. 21, 1962, Ser. No. 218,240 Claims priority, application Austria, Oct. 5, 1961,

A 7,495/61 5 Claims. (Cl. 179--115.5)

The electro-acoustic transducers used with dictating equipment are preferably adapted to take the dictation as well as to reproduce the same. This practice is suitable because it results in a reduced space requirement and in reduced costs. From the acoustic aspect, however, special measures must be adapted to ensure a satisfactory reproduction. Nevertheless, the dual-function transducers have been successful and it is now desired to improve the reproducing properties of such a transducer. This endeavour encounters difficulties because the space available in a handy, handle-shaped housing is relatively small, so that only transducers having the dimensions of usual microphones can be incorporated. Owing to their small size, these transducers must be overmodulated to obtain a sufficient volume of sound, and then give a distorted reproduction. For this reason it has been attempted initially to replace the small circular diaphragm by oval diaphragms of plastic sheeting or paper. The results, however, are not satisfactory because such diaphragms lack the stiffness required.

For this reason the invention proposes to use with dictating equipment a sound transducer which is characterized in that it is provided with a substantially flat diaghragm of foamed plastic, the rim of which diaphragm is suitably moulded to small thickness and is preferably molded with corrugations for increased resiliency, the diaphragm extending as far as to the rims of the housing part disposed above the change-over means. As a result, the diaphragm adjoins this housing part at the contour line thereof so that the space available can be utilized as fully as possible.

The moving coil is suitably centrically or eccentrically secured to the diaphragm so that an improved adaption to the space conditions is enabled.

It may also be suitable to give the diaphragm a slightly conical shape on the side facing the actuating system and a planar shape on the emitting side.

The diaphragm may also consist of a shaped body having stiffening ribs.

The advantages resulting from the use of a diaphragm of foamed plastic are truly surprising. The diaphragm of foamed plastic fully utilizes the space or area available for emitting sound. Where as it is still-er than concial diaphragrns of paper or plastic, it does not require a greater depth for installation. Besides, the diaphragm can be made at very low cost and when consisting of foamed plastic having a closed surface is absolutely insensitive to moisture.

An illustrative embodiment is shown in the figures of the accompanying drawing, in which FIG. 1a is a perspective View showing the foamed plastic diaphragm, FIGS. 1b, 1c, 1d are sectional views taken on line ab of FIG. 1 and showing transverse sectional forms of the diaphragm, FIG. 2a is a transverse sectional view showing a transducer according to the invention and FIG. 2b is a front elevation thereof.

As is shown in FIG. la, the diaphragm of foamed plastic has a shape which is adapted to the largest possible opening in the handle-shaped housing. The transverse sectional view of the diaphragm shown in FIG. 1b, taken on line ab of FIG. 1a, indicates that the main body of diaphragm has a relatively large thickness compared to the rim zone. The thickness ratio may be, e.g., 30:1 so that a diaphragm having a thickness of 3 mm. has a rim 0.1 mm. thick. This enables the provision of a very narrow rim zone so that the diaphragm itself has the largest possible area. To increase the elasticity, the rim zone may be moulded to have beads or corrugations although this is not essential.

FIGS. 2a and 2b show an illustrative embodiment of a handle microphone provided with the transducer according to the invention. The diaphragm 1 having a conical body, as shown in FIG. 1c, is adhered to the dome-shaped portion 2 of a small diaphragm provided with a moving coil The magnet systems and the switch gear or control means 4 consisting of push but tons 5 and slides 6 are known means for controlling the function of dictating equipment. A visual signal 7 serves for supervising the functions. Alternatively, the moving coil may be directly secured to the diaphragm of foamed plastic.

The sound transducer may be coupled to acoustic elements known per se to provide various directional patterns. For instance, the rear side of the diaphragm may communicate through connecting ducts with the openings at the rear side of the handle, or with the interior space of the housing. The first arrangement will result in a unidirectional pattern, the second in an omnidirectional one. A shutter, which may be connected to the slide 6, for instance, may serve for effecting an acoustic changeover so that a directional microphone is available for recording and a receiver having an omnidirectional pattern for the reproduction. The transducer may be surrounded by a housing (indicated by dash lines in FIG. 2a and provided with the reference numeral 8). To improve the frequency characteristic it is suitable to provide behind the diaphragm a low-volume air chamber, which is defined by a shell member 9 indicated in dotted lines. In addition to performing an electric switching operation, the slide 6 may be used to open and close openings in the shell member 8 and 9 and these openings may be provided with acoustic frictional resistances. In this case the transducer may be friction-controlled for recording and mass-controlled for reproducing sound.

I claim:

1. A sound transducer for dictating equipment comprising, in combination, a hollow, flat and shallow, and elongated handle shape microphone housing having an elongated opening in the upper portion of its front wall formed with a peripheral seat, the opening extending more than half the length of the front wall; control means mounted on said front wall on the lower portion thereof; a substantially flat molded diaphragm of foamed plastic closing said opening, said diaphragm having a relatively thick main body portion within said opening and bounded by a thin peripheral rim portion superposed on said peripheral seat; and a fiat and shallow drive system within the upper portion of said housing including a movable drive element in contact with a small area of the inner surface of the body portion of said diaphragm.

2. A sound transducer for dictating equipment comprising, in combination, a hollow, flat and shallow, and elongated handle shape microphone housing having an opening in the upper portion of its front wall formed with a peripheral seat; control means mounted on said front wall on the lower portion thereof; a substantially fiat molded diaphragm of foamed plastic closing said opening, said diaphragm having a relatively thick main body portion within said opening and bounded by a thin peripheral rim portion superposed on said peripheral seat; and a flat and shallow drive system Within the upper portion of said housing including a movable drive element in cont-act with a small area of the inner surface of the body portion of said diaphragm; said rim portion being formed with corrugations for increased resiliency.

3. A sound transducer for dictating equipment, comprising, in combination, a hollow, flat and shallow, and elongated handle shape microphone housing having an opening in the upper portion of its front wall formed with a peripheral seat; control means mounted on said front wall on the lower portion thereof; substantially flat diaphragm molded of foamed plastic closing said opening, said diaphragmhaving a relatively thick main body portion within said openingand bounded by a thin peripheral rim portion superposed on said peripheral seat; and a flat and shallow drive system within the upper portion of said housing including a movable drive element in contact with a small area of the inner surface of the body portion of said diaphragm; said diaphragm being planar on one side and having a shallow trapez'oid transverse section.

4. A sound transducer for dictating equipment comprising, in combination, a hollow flat and shallow, and elongated handle shape microphone housing having an opening in the upper portion of its front wall formed with a peripheral seat; control means mounted on said front wall on the lower portion thereof; a substantially flat diaphragm molded of foamed plastic closing said opening, said diaphragm having a relatively thick main body portion within said opening and bounded by a thin peripheral rim portion superposed on said peripheral seat; and a flat and shallow drive system within the upper portion of said housing including a movable drive element in contact with a small area of the inner surface of the body portion of said diaphragm, said diaphragm consisting of a shaped body formed with stiffening ribs.

5. A sound transducer as set forth in claim 1, in which said drive system is of electrodynamic type.

References Cited by the Examiner UNITED STATES PATENTS 1,918,422 7/1933 Nystrom 181-32 2,297,218 9/ 1942 Henrich et al. '18132 2,905,260 9/1959 Williams 181-32 2,926,741 3/1960 Rohn et al. 181-32 3,035,132 5/1962 Gorik-e et al. 179--167 3,052,785 9/1962 Herrmann et'al. 179-167 FOREIGN PATENTS 513,289 10/1939 Great Britain.

ROBERT H. ROSE, Primary Examiner. 

1. A SOUND TRANSDUCER FOR DICTATING EQUIPMENT COMPRISING, IN COMBINATION, A HOLLOW, FLAT AND SHALLOW, AND ELONGATED HANDLE SHAPE MICROPHONE HOUSING HAVING AN ELONGATED OPENING IN THE UPPER PORTION OF ITS FRONT WALL FORMED WITH A PERIPHERAL SEAT, THE OPENING EXTENDING MORE THAN HALF THE LENGTH OF THE FRONT WALL: CONTROL MEANS MOUNTED ON SAID FRONT WALL ON THE LOWER PORTION THEREOF; A SUBSTANTIALLY FLAT MOLDED DIAPHRAGM OF FOAMED PLASTIC CLOSING SAID OPENING, SAID DIAPHRAGM HAVING A RELATIVELY THICK MAIN BODY PORTION WITHIN SAID OPENING AND BOUNDED BY A THIN PERIPHERAL RIM PORTION SUPERPOSED ON SAID PERIPHERAL SEAT; AND A FLAT AND SHALLOW DRIVE SYSTEM WITHIN THE UPPER PORTION OF SAID HOUSING INCLUDING A MOVABLE DRIVE ELEMENT IN CONTACT WITH A SMALL AREA OF THE INNER SURFACE OF THE BODY PORTION OF SAID DIAPHRAGM. 